The use of an electronic flash unit for photography is very well known. The main components of an electronic flash unit are a flash circuit board, a through-shaped flash reflector, a flash tube positioned within the flash reflector, and a transparent or translucent flash cover-lens. The flash reflector, the flash tube and the flash cover-lens are mounted on the flash circuit board. The flash reflector is shaped to concentrate the flash light produced by the flash tube and to direct the flash light through a front open end of the reflector towards the subject to be illuminated. The most efficient shape of the reflector is a parabola which concentrates the flash light into a beam that may have parallel, converging or diverging rays according to whether the flash tube is at the focal point of the parabola, in front of the focal point, or behind the focal point. The flash cover-lens covers the front open end of the flash reflector and can act as a light diffuser, softening the flash light and spreading it more evenly over the subject to be illuminated.
The flash tube is filled with an ionizable gas, and it has an in-line pair of anode and cathode main electrodes at its opposite ends which protrude from respective side openings in the flash reflector and are connected to a capacitor on the flash circuit board. The resistance of the gas in the flash tube is normally too high to permit a direct discharge. For firing the flash tube, there is provided a third electrode, i.e. a triggering electrode, for example a triggering wire that is connected to an outer side of a rear closed end of the flash reflector using solder, tape or the like. The flash reflector often is located in a hole or cut-out in the flash circuit board and the rear closed end of the flash reflector protrudes from the hole or cut-out. The flash tube is urged against an inner side of the rear closed end of the flash reflector, such as by an elastomeric band. When the triggering electrode applies a triggering voltage to the flash reflector, the gas in the flash tube is ionized, thus lowering its resistance and allowing the capacitor to discharge its stored energy through the flash tube in the form of a flash of light. See prior art U.S. Pat. No. 4,223,372 issued Sep. 16, 1980, U.S. Pat. No. 5,047,900 issued Sep. 10, 1991, and U.S. Pat. No. 5,436, 685 issued Jul. 25, 1995.